Question Help with undervolting MSI H97 Gaming 3's PCH

Apr 7, 2021
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I want to undervolt PCH on my motherboard to make the mobo's life easier but i got a couple of questions.
There are two PCH options in the UEFI: PCH 1.05 and PCH 1.5. I don't understand what the difference between them is, can you explain? One is for northbridge, the other one for southbridge?
I set PCH 1.05 to 1V and PCH 1.5 to 1.4V, everything works super stable (even when using around 7 USB ports). Can someone please clarify that PCH 1.5 actually runs at 1.5V stock? Just in case i know that undervolting has been done correctly and i'm not frying anything.
Also, i run RAM at 1T command rate which is, again, stable but how does lowering PCH voltage affect stability of that setting? As i know the northbridge has to be somehow resposible for command rate, does it have to do anything with PCH at all?
 
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JWNoctis

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PCH, or Platform Controller Hub, is basically southbridge in old parlance. As far as I'm aware, you shouldn't need to touch its voltage, or anything. They don't dissipate much power either way, undervolting or not. It had nothing to do with system memory, or northbridge, which has been integrated inside the CPU package for more than a decade.
 
Reactions: HeartOfAdel
Apr 7, 2021
33
1
35
0
PCH, or Platform Controller Hub, is basically southbridge in old parlance. As far as I'm aware, you shouldn't need to touch its voltage, or anything. They don't dissipate much power either way, undervolting or not. It had nothing to do with system memory, or northbridge, which has been integrated inside the CPU package for more than a decade.
Why is it divided into PCH 1.05 and PCH 1.5 then?
And anyway, even if it didn't require much power, slight undervolting would still be better than stock i believe.
And is there a way to undervolt the Northbridge?
 
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JWNoctis

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Why is it divided into PCH 1.05 and PCH 1.5 then?
And anyway, even if it didn't require much power, slight undervolting would still be better than stock i believe.
And is there a way to undervolt the Northbridge?
Per the datasheet of the chipset here, your H97 chipset required three voltages to function: 1.05V, 1.5V, and 3.3V. The power supply range for 1.05V rail is 0.998V - 1.10V, while the one for 1.5V rail is 1.43V - 1.58V.

And no, undervoltaging that would not be better than stock. There's nothing to gain here except for a possible minimal increase in lifespan of your chipset, in exchange for much greater risk of BSOD and data corruption.

Intel CPU and MB haven't had a discrete northbridge since Nehalem microarchitecture. There are plenty of articles you could research on about every tech site, if it is your CPU that you want to undervolt.
 
Reactions: HeartOfAdel
Apr 7, 2021
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Per the datasheet of the chipset here, your H97 chipset required three voltages to function: 1.05V, 1.5V, and 3.3V. The power supply range for 1.05V rail is 0.998V - 1.10V, while the one for 1.5V rail is 1.43V - 1.58V.

And no, undervoltaging that would not be better than stock. There's nothing to gain here except for a possible minimal increase in lifespan of your chipset, in exchange for much greater risk of BSOD and data corruption.

Intel CPU and MB haven't had a discrete northbridge since Nehalem microarchitecture. There are plenty of articles you could research on about every tech site, if it is your CPU that you want to undervolt.
Thank you very much for your help. I do think that stability is important but if PC works perfectly fine with those voltages then there's no reason to get it back.
I have one more question. You listed the power supply range for the two railes, does it mean that i can't get voltages outside for example 1.43V-1.58V for 1.5 rail? Because i put it to 1.4V. Does it affect PSU in any way?
 

JWNoctis

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Jun 9, 2021
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Thank you very much for your help. I do think that stability is important but if PC works perfectly fine with those voltages then there's no reason to get it back.
I have one more question. You listed the power supply range for the two railes, does it mean that i can't get voltages outside for example 1.43V-1.58V for 1.5 rail? Because i put it to 1.4V. Does it affect PSU in any way?
It's actually a bit surprising that your BIOS allowed you to change PCH voltage at all. I assume it's used for calibration since voltage settings does not necessarily match what's actually supplied by VRM on your motherboard.

I don't think a 5W TDP part would affect your PSU in any meaningful way.
 

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